WASHINGTON -- President Donald Trump went too far when he falsely claimed that former President Barack Obama had not called the families of slain soldiers, former Attorney General Eric Holder said Wednesday.

"Mr. President, you crossed the line there," Holder said.

The former Democratic prosecutor continued: "And you know, I understand you've got a tough job. I generally hold my powder, but that was a line that you crossed."

Holder, a top ally of Obama's who was attorney general for the first six years of his presidency, said Trump's comments made him feel he needed to speak out.

"To imply that President Obama was not appropriately sensitive, was not appropriately involved, was something that I was simply not going to allow to go unaddressed," Holder said. "That made me mad in a way that few other things have."

At a news conference Monday, Trump said Obama and other presidents didn't make calls to families of fallen soldiers, and when pressed on the point said, "I was told that he didn't often."

Holder reacted strongly on Twitter, saying the president should "stop the damn lying."

The next day, Trump invoked his chief of staff, John Kelly, whose son died in Afghanistan.

"You could ask Gen. Kelly, did he get a call from Obama?" Trump said.

Trump has since challenged the account of a Democratic congresswoman who said the president was disrespectful in a phone call to the widow of a dead soldier. A family member said the congresswoman's account was accurate.

In Wednesday's interview, Holder said that as attorney general he had to make condolence calls to families of agents who lost their lives in the line of duty.

"Those interactions in some ways I think reveal you for who you are," Holder said.